ON A windswept day in 1922, around 100 Mennonite families unloaded their few possessions, their horses and carts and their precious hand- me-down Bibles, in the middle of the barren plains of northern Mexico. As the convoy of trains that had brought them from Canada moved off, many must have feared they were making a terrible mistake. Today, more and more of their descendants are reaching that conclusion. Some have gone back where they came from. Some have, literally, gone to pot.

The transition from Canada to Mexico was to prove the most traumatic leg of a journey that had started in 16th-century Europe. The German-speaking Mennonite migrants were fleeing post-war anti-German hostility in what was at the time still a British colony. They had not wanted to fight for Canada, or for anyone - they have religious objections to warfare - and had resisted threats to conscript their youth. But in Mexico, the Mennonites found themselves, if anything, even more out of place: shy, simple folk, they were blue-eyed blonds among dark-skinned mestizos and Indians, pacifists in a land recovering from a bloody seven-year revolution, Protestants in a nation of Catholics.

The new immigrants adapted and set about living as their forefathers had, building simple dwellings, first of wood, later of adobe, turning the other cheek when their communities were raided in the post-revolution social unrest that still simmered. They bought land at $8.25 an acre; founded settlements with names like Manitoba Colony and Swift Current to remind themselves of home; tilled the unyielding land until they produced corn, beans and oats; resisted contact with the Tarahumara Indians and other Mexicans in the Cuauhtemoc area; maintained their own language (Plattdeutsch, or Low German), culture and schools; and refused to use motorised transport. As they carved out their lives, the men stuck to their traditional blue- bib overalls, and the women to their black headscarves, cotton frocks, white stockings, black shoes, and bobbed, fringed hairstyles.

Their ancestors had come from Friesland, in the Netherlands. They were followers of Menno Simons, a priest who renounced Catholicism after being caught up in the Anabaptist movement, a radical Protestant sect, that swept north from Switzerland at the time of Martin Luther. So moved was Simons by hearing Anabaptist prisoners singing hymns before being executed by the Spanish Inquisition (the Netherlands were then ruled by Spain) that he joined their cause and became their leader. This year, the descendants of his followers, the Mennonites, are celebrating the 500th anniversary of Simons's birth.

Today, there are at least 500,000 Mennonites around the world, notably in Mexico, Canada, the United States, Bolivia, Paraguay, Argentina and Belize. As Simons and other Anabaptists did five centuries ago, they oppose infant baptism, insisting that church membership be granted only to those who have proved their goodness through their actions. Like the Amish, the Shakers and other puritan sects, they place great emphasis on the value of a simple life, eschewing many trappings of the modern world. Unfortunately, the severity of Mexico's economic crisis and the moral snares of the late 20th century have pushed at least a few of their members into temptation, and into jail.

GREETING the US customs officers with a cheery "Buenos dias", Jacobo Froesse-Friessen looked as harmless as they come as he drove his empty grain lorry across the Rio Grande from Mexico's Ciudad Juarez into El Paso, Texas. It was 4.30am on 21 April last year and the 31-year-old said he had come to buy fertiliser for his north Mexican farm. With his Mennonite overalls and fair skin, the farmer might have expected to be waved through, but for two little problems. One: a customs dog was reacting to something it smelt behind the lorry's side panels. Two: Mr Froesse-Friessen's community may have renounced material things, but more than 30 Mennonites had already been arrested at the US or Canadian borders over the previous five years for smuggling marijuana. And that was what the German shepherd had recognised. The lorry was carrying 101 bundles of fresh marijuana, weighing 760lbs. It was the biggest haul ever from a Mennonite, and Froesse-Friessen was sentenced last October to six years in jail followed by five years' probation.

US customs officers suspect Froesse-Friessen of being part of what they call the Mennonite Connection, a ring of marijuana smugglers from communities in Mexico, the US and Canada. The first "Mennonite" haul was uncovered in 1989, when furniture being trucked into El Paso by a Mennonite called Cornelius Banman was found to have been hollowed out to contain 238lbs of marijuana. Now, customs officers estimate that 20 per cent of the Mexican marijuana which reaches Canada is carried by Mennonites. The Mennonites themselves insist that the smugglers are a tiny minority of their community (perhaps 100 out of the 50,000 in Mexico), and while not condoning the crimes, see them as the result of a series of economic disasters and drought.

Whatever the numbers, the fact that even a few members of such a traditionally austere community are smuggling and smoking marijuana has pushed worries about the escalating culture clash with the modern world into fear for of the sect's very survival. Only a few campos (Mennonite villages) still spurn electricity and use only horse-drawn carts; most have moved into the 20th century, complete with cars, pick-up trucks, tractors, TVs and video. And now young men, fuelled by alcohol, go "cruising" in town on Saturday night just like their Mexican counterparts, wearing baseball hats, jeans and cowhide boots in preference to the traditional overalls and plain shirt.

It was, perhaps, inevitable. The Mennonites in Mexico have always, in their own way, moved with the times. First they became virtually self- sufficient, eking out a living from their corn, beans, oats, sorghum, milk and "Queso de Chihuahua" (cheese). Then they expanded their interests, becoming known for making and selling furniture, stoves and parts for agricultural machinery. They reached their economic peak during Mexico's boom years in the Eighties - that's when the tractors were bought and the microwaves began appearing in their kitchens. But the Nineties brought severe drought - and crop failure. Then, in January 1994, came new restrictions under the North American Free Trade Agreement (Nafta) which meant an end to the Mexican government subsidies that guaranteed the Mennonites profits from their products. Finally, there was the collapse of the peso (in December 1994), which has more than doubled their outlay on equipment, fuel and raw materials. The Mennonites have been particularly hit by this recession because of their high birth rate. Contraception is a taboo, and their numbers double every 15 years; as a result, the 100,000 acres they originally bought from the Mexican state is no longer enough to go around.

But the problems are not solely economic. "There's been a general deterioration in education. There's disrespect for traditional norms," said Tony Enns, a Canadian Mennonite who heads the Winnipeg-based Mennonite Central Committee (MCC). The organisation was set up to distribute overseas aid to non-Mennonites worldwide, but is now addressing itself to the problems of the Mexican Mennonites. "There's been some abuse," he went on. "There's been some incest. Drunkenness is a concern. There's some chasing girls, going after prostitutes, that kind of thing. They buy beer and bring it back to their villages." Another MCC leader, Abe Warkentin, went further, describing the situation in Mexico as "one of the greatest tragedies of Mexican history". He sees a spiritual bankruptcy. "I am haunted by illiterate children, by the suicides, by the drug busts and by the immorality." (At least two Mennonite women are known to have hanged themselves last year.)

Of course, one man's immorality is another man's movement with the times. Normando Perales, an assistant to the mayor of Cuauhtemoc, had his own explanation of the Mennonites' condition. "They're a community in transformation," he said. "They were part of the creation of this town but their socio- economic integration began only around 15 years ago. There have been a few inter-marriages; some even come to Mexican schools. I think the problem of alcohol among their youth is down to the restrictions they're used to. There's nothing more attractive than the forbidden."

One young Mexican engaged to a Mennonite girl is Cristobal Fierro, a 24-year-old sales representative. "They're changing. My fiancee's parents accept me and that I'm going to be living with her outside their community, in our own flat, after we are married. She had already converted to Catholicism before we met. But they've got to change and be more outgoing. If they don't, we guys are just going to go in there and steal them away."

The thought of marriage outside the community, however, is still anathema to most Mennonite parents. Sitting at the dining table in her clean, comfortable home in Campo 2A in the conservative Manitoba Colony outside Cuauhtemoc, 17-year-old Anita Harms told me that she accepted that she would have to marry a Mennonite despite her dreams of becoming a singer of Mexican ranchero songs - wailing ballads of love, infidelity and drunken husbands.

"There's no choice," she said. "It's the religion. They don't want to mix the religions. I don't agree. I think God made us all equal. I think it would be good to mix."

Alone on her parents' farm - her father was away helping a fellow farmer burn his cornfield, while her mother, brother and sister were at Bible study - Anita showed us round what would be a luxurious home to many Mexicans. The floor was covered with linoleum and the furniture was basic, but there was also an upright piano, an electric organ, a TV set with video recorder, a stereo hi-fi, a man-sized refrigerator and deep freeze, a microwave oven and even a modern electric treadmill that her 45-year-old mother Martha uses to keep fit. Anita had her own bedroom, with a quilted bedhead, pink trimmings, a poster of the American country singer John Michael Montgomery and photographs of teenage friends kissing and drinking beer at parties.

Anita sat, her head uncovered, her blonde hair falling to her shoulders, wearing lipstick and earrings. She never laughed, rarely smiled, and admitted that boredom was her main enemy. "Sometimes I wish so much that I were Mexican," she told us in the High German she had learnt at school to complement the Low German she speaks at home. "Their lives are so much easier. They can make friends with each other. Here, there's nothing to do. I'm bored to death on weekends. The boys go out and buy beer and drink it by the roadside. Sometimes girls go, too, but I don't like it." Everybody knew people involved in drug smuggling, she said. "There're a lot of them around, even here. We know who some of them are, but not all of them. There's a man in the house up the road who's a smuggler."

Whether the Mennonite smugglers have their own mafia or are being used by Mexican or American drug lords is a matter of debate among the US Customs officers I spoke to. "We caught another one last week," said Roger Maier, spokesman for the El Paso office of US Customs & Immigration. "I don't think they're very well organised. In questioning them, we haven't come up with anyone who may be behind it." That may be the official line, but, in an informal chat at the old Cordova bridge checkpoint between Ciudad Juarez and El Paso, customs officer Grant Milner expressed other opinions: "There's a ring all right," he said. "There are a lot of them and they'll smuggle marijuana any way they know how. They may look like simple people but they're not one bit naive. These guys are specialists."

Most Mennonites, of course, are horrified by the very idea of such activities. The difficulty is knowing what to do about them. One Mexican Mennonite who is trying to attack his community's problems - drugs, alcohol, integration and so on - is Abram Siemens. Forty-year-old Siemens presents a nightly Low German-language radio programme from the local Mexican station XEPL. The community's traditions and sensitivities mean that he has to tread softly; for instance, he mentions drugs only when he has concrete evidence, such as a drug bust in El Paso. Recently, after he mentioned the name of an arrested Mennonite on air, he received a death threat.

Because of his radio programme, Siemens is an unofficial spokesman for the Mennonite communities. "As for drugs, everybody in the world can be tempted if offered enough. The people keep asking me to tell foreign journalists like you to concentrate on the demand, the demand for drugs in the US, Europe or Canada. They ask me to tell you this, 'Look at what your demand is doing to us. People on the other side of the border are doing everything to corrupt us.' These big mafia drug lords in Latin America have bigger bosses in the US. The buyer always has the last word. The people here want me to tell you, 'Focus on the demand'. They don't think their community is rotten. They agree something needs to be done but they're annoyed that they're getting such a bad image from a few. And this causes problems for all Mennonites now when they cross the borders into the US or Canada. We have so few different names. Although we're not related, many of us have the same surnames, and there are only about 10 Christian names that we use. So we're often confused with convicted drugs smugglers at the border."

But Siemens senses a deeper malaise. "People here seem to be unhappy with what they have," he says. "It could be a sign of indifference to moral values. But I think the alcohol problem is exaggerated here. Because the young people don't have recreation halls, they drink in the street, so it's visible and people talk about it. Plus, you don't expect Mennonites to drink at all. You expect them to be perfect. But you have to accept we're human."

Abram Siemens may have a point, but being human can have a depressing side. As I strolled down Victoria Street in the state capital of Chihuahua, a group of young men in American baseball jackets and caps accosted me on the pavement outside the San Juan bar. Clutching bottles of Carta Blanca beer, they swayed gently and amiably questioned me in broken English. Two passing Mexicans looked disdainfully on. "Ignore them," one urged me. "They're Mennonites. They can't hold their liquor." It was not what Menno Simons would have wished for. !